The compound represented by the above-mentioned general formula (I), namely the objective compound of the present invention, is known to be useful as an antithrombotic agent, a cerebral circulation improver, an anti-inflammatory agent, an antiulcer agent, a hypotensive agent, an antiasthmatic agent, and a phosphodiesterase inhibitor, etc. (see: JP-A-56-49378 and U.S. Pat. No. 4,277,479).
The carbostyril derivatives represented by the general formula (I) have so far been produced by reacting a carbostyril derivative represented by the following general formula (II):
wherein the bond between the 3- and 4-positions of the carbostyril skeleton is as defined above, with a tetrazole derivative represented by the following general formula (III′):
wherein X′ represents a halogen atom, and A and R are as defined above, in the presence of an inorganic base or an organic base (see: JP-A-56-49378; U.S. Pat. No. 4,277,479; and Chem. Pharm. Bull., 31(4), 1151-1157 (1983)).